The makers of Bethenny Frankel’s Skinnygirl Margarita should pay $10 million for being big fat liars, a new lawsuit says.

In papers filed in Manhattan federal court yesterday, Christopher Rapcinsky and Erin Baker say they were duped into buying the “Real Housewives of New York City” star’s pricey potable because it was billed as “all natural” with “no preservatives.”

Frankel (left) said the “margarita you can trust” only had two ingredients: agave nectar and tequila.

Rapcinsky and Baker found out that wasn’t the case after news that Whole Foods was yanking the ready-made cocktail from its shelves because it contained the potentially toxic synthetic preservative sodium benzoate.

Now they’re the lead plaintiffs in a proposed class-action lawsuit seeking money damages on behalf of all Skinnygirl customers — and looking to force the drink’s producers, Beam Global, to change the label.

“It could say, ‘nearly natural’ or ‘almost no preservatives,’ but it doesn’t,” said the customers’ lawyer, Thomas Mullaney. “It’s clearly misleading.”

He said his clients and people like them had paid premium prices for Skinnygirl — about $19 a bottle — because they thought it was free from chemicals.

“There are a handful of other margarita products out there that are not as expensive as Skinnygirl, but people paid up because they wanted something that was not going to be unnatural,” Mullaney said.

A rep for Beam Global — which bought the 2-year-old beverage line from the “Bethenny Ever After” star for a reported $120 million earlier this year — said, “In today’s litigious society, nothing is surprising,” and called the suit and a similar one that was filed in California “frivolous.”

Frankel has also shrugged off the controversy, saying, “We were bound to piss someone off, and everyone loves to try to tear down a success. This is a non-event.”